Light-weight disc brake

ABSTRACT

The brake shoes of a disc brake having a light-metal housing are supported in a circumferential direction and are axially slidable on supports which are fixed to the housing and made of a high-strength material. The supports are cast into the housing and supporting surfaces for the brake shoes are then shaped in a subsequent machining operation.

BACKGROUND OF THE INVENTION

The present invention relates to a disc brake having a housing made oflight metal.

German patent application No. 38 03 957 discloses a disc brake of thistype. The prior art disc brake has a low-weight housing cast fromaluminum. This is favorable especially with respect to reducing theunsprung masses on the vehicle wheel. A disadvantage of light-metalhousings of this type is that corrosion and increased wear occurs at thepoints of support for the brake shoes. The reason is to be seen in thematerial of the brake shoe backing plates which almost exclusivelyconsist of iron. Therefore, profiled rails are provided in the prior artdisc brake on which the brake shoe backing plates are supported. Theprofiled rails are screwed to the housing. This type of attachmentpermits compensating for manufacturing tolerances because the profiledrails are adjusted within the limits of a predetermined clearance and,subsequently, may be fixed in the optimal position by the screws.

The problem of the brake shoe support in light-metal housings in theprior art disc brake is satisfactorily overcome as far as the technicalfunction is concerned. However, the solution is very costly becauseprofiled rails with a complicated shape are used, and the attachment byscrews with a tolerance compensation also causes increased manufacturingcosts.

SUMMARY OF THE INVENTION

An object of the present invention is to improve a disc brake having alight-metal housing so that a simple assembly which is inexpensive tomanufacture is achieved especially with respect to the support of thebrake shoes.

This object is achieved by casting in the supports fixed to the housingwhich are made of a high-strength material and provided to support thebrake shoes already when casting the light-metal housing, andcompensating for the tolerances, which occur in the manufacture, in asubsequent machining operation when the supporting surfaces for thebrake shoes are shaped into the supports. In the disc brake according tothe present invention, the machining operation for the supportingsurfaces, which is also required in the state of the art disclosed inGerman patent application No. 38 03 957, is postponed until after thesupports are attached in the housing. This renders it possible to castthe supports into the housing and to initially tolerate the occurringmanufacturing tolerances which will be compensated in the subsequentmachining operation. The effort needed in the state of the art for theadjustment of the supports is also eliminated in the disc brakeaccording to the present invention. The proposed configuration of thesupporting surfaces as cylinder segments arranged coaxially relative toa brake cylinder bore of the housing allows a subsequent machining ofthe housing in one machining operation with a cylindrical tool.

Favorable materials for the housing are aluminum or aluminum alloys. Forthe supports, stainless steel or titanium are appropriate.

The present invention can be implemented in a particularly favorablefashion in a disc brake as disclosed in German patent application No. 4036 063. The prior art disc brake has a housing made of iron materialwherein supports for the brake shoes are formed. After casting thehousing, the supporting surfaces of the supports are favorably machinedin one operation simultaneously with the manufacture of the brakecylinder bore. Preferred aspects of the present invention relate to adisc brake having a housing shape as disclosed in German patentapplication No. 40 36 063.

In simple embodiments of the present invention, which are especiallyinexpensive to achieve, the supports are configured as pins or as hollowtubular members for further weight reduction.

In a preferred aspect of the present invention, the supports themselvesare supported by piled-up materials of the housing on the sides lyingoutwards in a circumferential direction. In this embodiment, thesupports themselves may have a weaker design, with the result thatmaterial costs and weight are further reduced. The sole issue which issignificant to the present invention is that the supporting surfaces forthe brake shoes are made of a relatively non-abrasive andcorrosion-resistant material.

At least one lateral surface or a hexagonal shape of the supports arefavorable arrangements for the form-locking and unrotatable fixation ofthe supports in the brake housing.

One embodiment of the present invention will be explained in detailhereinbelow making reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing,

FIG. 1 is a lateral view of a housing blank for a disc brake accordingto the present invention.

FIG. 2 is a partial cross-sectional top view of the same blank takenalong line A--A in FIG. 1.

DETAILED DESCRIPTION OF THE DRAWING

A housing part 1 cast from aluminum is shown in the drawing. A blank inthe condition in which it was cast is shown. Two supports 2, 3 ofstainless steel are cast in the housing part 1. A brake shoe 4 can besupported on the supports 2, 3. In a preferred aspect of the presentinvention, the supports 2, 3 are made of titanium. Compared to supportsmade of stainless steel, this arrangement is favorable when the aluminumhousing is treated in eloxal process.

As can be seen in FIG. 2, the brake shoe 4 which includes a backingplate 5 and a friction lining 6 is shown in the non-assembled condition,because its mounting is not yet possible prior to the subsequentmachining of the housing part 1.

The supports 2, 3 are configured as tubular members, each including anannular groove 7 for fixation in the material of the housing part 1. Onthe sides of the housing part 1 which are disposed outwardly in acircumferential direction, the supports 2, 3 in turn are supported bypiled-up materials 8, 9 to achieve a higher load-carrying capacity forthe circumferential forces which occur at the brake shoes 4 duringbraking. The housing blank further accommodates a brake cylinder 10having a hollow space 11 intended for the later accommodation of thebrake piston, which is not shown.

In a subsequent machining operation, a brake cylinder bore 12, shown indotted lines in FIG. 1, is shaped in the hollow space 11 of the brakecylinder 10. The drilling tool used has a stepped design so that twosupporting surfaces 14, 15 of the supports 2, 3 can be machined with theradius 16 apart from the brake cylinder bore 12 with the radius 13.Thus, the supporting surfaces 14, 15 of the supports 2, 3 have the shapeof cylinder segments which are arranged coaxially relative to the brakecylinder bore 12 of the housing 1.

We claim:
 1. A disc brake having a housing of light metal and includingbrake shoes, which are supported in a circumferential direction onsupports of high-strength material fixed to the housing and which areslidable in an axial direction, wherein the supports are cast into thehousing and include supporting surfaces each defined by a common radius,wherein said supporting surfaces are configured as segments of a commoncylinder, wherein said cylinder is arranged coaxially relative to abrake cylinder bore of the housing wherein the supports are configuredas tubular members.
 2. The disc brake as claimed in claim 1, wherein thehousing is made of aluminum or an aluminum alloy.
 3. The disc brake asclaimed in claim 1, wherein the supports are made of stainless steel. 4.The disc brake as claimed in claim 1, wherein the supports are made oftitanium.
 5. The disc brake as claimed in claim 1, wherein the supportsare configured as pins.
 6. The disc brake as claimed in claim 1, whereinthe supports themselves are supported by piled-up materials of thehousing on the sides which are disposed outwards relative to a brakeshoe in a circumferential direction.
 7. A disc brake having a housing oflight metal and including brake shoes, which are supported in acircumferential direction on supports of high-strength material fixed tothe housing and which are slidable in an axial direction, wherein thesupports are cast into the housing and include supporting surfaces eachdefined by a common radius, wherein said supporting surfaces areconfigured as segments of a common cylinder, wherein said cylinder isarranged coaxially relative to a brake cylinder bore of the housing,wherein said supports are supported by piled-up materials of the housingon the sides which are disposed outwards relative to a brake shoe in acircumferential direction.